Previous work from our laboratory has revealed a highly interactive and complicated redox potentiometric behavior involving all of the redox centers in mammalian cytochrome aa3. Although all of the redox centers are on 2 subunits, the enzyme has 13. Perhaps the additional peptides are responsible for this complexity. To test this idea, we examined a natural 2 subunit cytochrome aa3 isolated from Paracoccus denitrificans. It was found that all of the complicated behavior was present with the structurally simpler enzyme. Therefore, the observed redox pattern must be related to the necessary energy transduction function of the enzyme. A new system for automated electrodic potentiometry was developed using the IBM PS2/80 computer with all of the software written in the language of "C". Steps were taken to design and build a new kind of rapid scan spectrometer. This instrument will be able to take a continuous series of optical spectra every 10 (mu)sec. These spectra will be examined by SVD to define the kinetic sequence of intermediates during cytochrome aa3 turnover. A new collaborative project was initiated to combine potentiometry and absorption spectroscopy with Resonance Raman spectroscopy in order to learn more about events taking place at redox centers during oxidation and reduction.